1. Field of the Invention
This invention pertains generally to devices and methods for cutting, boring and reaming pipes or tubes, and more particularly to a rotary pipe cutting apparatus for removing portions of broken plastic pipe from the bore of an outer pipe.
2. Description of the Background Art
The use of plastic pipe for irrigation and landscape sprinkler systems has become widespread due to the lower cost of plastic pipe compared to galvanized metal pipe. Polyvinyl chloride (PVC) and acrylonitrile-butadiene-styrene (ABS) plastics are the most widely utilized materials for fabrication of plastic pipes. One drawback associated with plastic pipe, however, is that it provides lower strength than galvanized metal pipe, and thus irrigation and sprinkler systems employing plastic pipe can be more prone to breakage and require more frequent repair. A common example of this problem is provided by a standard lawn sprinkler systems wherein a sub-ground plastic pipe network includes several "T" fittings which extend upward towards the ground surface for attachment of sprinklers. The sprinklers are generally attached to the "T" fittings by means of a plastic riser pipe sized to fit within the inner diameter of the "T" fittings and which are glued into the "T" fittings. If a sprinkler is inadvertently kicked or struck by a lawn mower or bicycle, the plastic riser pipe may break off and leave a broken portion glued within the "T" fitting. The broken portion of riser pipe prevents attachment of a new riser and sprinkler to the "T" fitting. To repair the break and replace the sprinkler, one must dig around the "T" fitting, cut the pipe around the "T" fitting, and then install couplings, a short length of pipe, and a new "T" fitting. This procedure is expensive, time consuming, and inconvenient. The use of threaded risers and "T" fittings has been introduced to facilitate the replacement of broken risers, but the broken threaded portions of such risers often cannot be successfully be removed from the threaded "T" fitting without damaging the "T" fitting, and thus the above-described inefficient procedure must still be used.
Several cutting, reaming, boring and chamfering tools have been developed to aid in removal of broken sections of plastic pipe from the bore of an outer pipe or pipe fitting. Typically, such tools are rotary in nature and employ one or more blades which cut or grind away the inner, broken pipe portion from the outer pipe. The currently available cutting devices, however, have proven deficient for various reasons. Particularly, the presently used devices are difficult to guide and control during cutting, and can damage the outer pipe during removal of the broken inner pipe. Another problem is that the individual devices are usually configured to remove an internal broken pipe portion of only a certain wall thickness or size, and cannot effectively remove inner pipe with a different wall thickness. Still another problem experienced with currently used cutting devices is that the shavings or turnings produced during cutting are not directed away from the cutting site but, instead, tend to be retained adjacent the blade or blades, and thus the device must periodically be withdrawn from the outer pipe during a cutting operation to clean the blade or blades and remove shavings.
Accordingly, there is a need for a rotary pipe cutting apparatus which provides for removal of broken plastic pipe from an outer pipe, which does not damage the outer pipe, which can be used to remove broken pipe of different wall thickness, and which does not cause buildup 5 of shavings adjacent to the cutting blade or require periodic removal of shavings during a cutting operation. The present invention satisfies those, needs, as well as others, and generally overcomes the deficiencies found in the background art.